Method and sampler for taking an undisturbed soil sample



States Patent US. Cl. 175-59 7 Claims ABSTRACT OF THE DISCLOSURE The sampling means is comprised of a hose, an outer tube, an inner tube, means for inserting the sampling means into soil, means for closing off the hose end, a supporting liquid and means for removing the soil sample from the soil. The hose is deformable in the transverse direction and has little deformability in the longitudinal direction. The deformation in the transverse direction is inversely dependent upon the amount of stress on the hose in the longitudinal direction. The inner tube is disposed within the outer tube. The hose is partially contained in the annular chamber formed between the inner and outer tubes. The inner tube has a circumferential exit port through which the annular chamber communicates with the interior of the inner tube. Upon insertion of the sampling means into the soil, the soil sample penetrates within the inner tube, pulls the hose through the exit port and out of the chamber and contains itself at one end within the hose. The hose is closed off at the other end so as to encase the soil sample within a portion of the hose without exerting a substantial pressure on the sample and while maintaining the closed end of the hose at a constant level in respect of the surrounding soil. The supporting liquid i contained between the inner tube and the hose. The hose is substantially impervious to the supporting liquid and to the components of the sample. The supporting liquid causes the hose to be pressed against the chamber wall. The sample is removed from the soil while maintaining sufficiently high friction between the hose and the exit port so that the longitudinal tensile load of the hose together with the hydrostatic pressure of the supporting liquid is sufficient to prevent outward deformation of the sample.

The invention relates to a hose intended for taking an undisturbed soil sample, to a method and a sampler for applying such a hose, and to a process and an apparatus for manufacturing such a hose.

It is known to use a knitted pipe for taking a soil sample, which pipe is present in folded condition in a chamber, said chamber being concentrically arranged around a tube into which the soil sample penetrates the soil sampler. At its lower end said chamber communicates with the interior of said tube by means of a circumferential slit. The knitted pipe is pulled through said slit out of the chamber and is closed off by binding or pinching. By means of a string or the like extending through the sampler and connected to said hose said closed end may be maintained at a constant level in respect to the surrounding soil. During the penetration of a soil sample, said knitted pipe will, therefore, not move in respect to this sample. In this manner the composition of the soil is prevented from being modified by the friction against the inner wall of the sampling tube.

Such a knitted pipe should, on the one hand, he pliable and transversely stretchable, since the chamber in which said pipe is stored has a larger diameter than the sample.

3,51 1,324 Patented May 12, 1970 On the other hand said knitted pipe should remain tightly around the sample after having been pulled through the slit, without, however, exerting a substantial pressure on said sample.

However, since the deformability of such a knitted pipe in the transverse direction is considerable, no resistance against a transverse deformation of the sample is offered. Moreover, the friction between such a pipe and the wall of the sampling tube is considerable, especially in the case of long samples. To this purpose a so-called supporting liquid is generally used, producing a friction reducing layer between the wall of the tube and the sample and exerting, simultaneously, a counter pressure on the sample. It will be clear that said counter pressure may act effectively on the sample only in the case where the latter shows a sufiicient coherence or the knitted pipe itself forms a closed separating wall between the liquid and the sample. The latter condition is, moreover, necessary when there is a danger of the supporting liquid to cause a modification of the water content or the composition of the sample. Therefore, a liquid is often provided in the store chamber of the hose which may seal off the meshes thereof. As soon as the last mentioned liquid contacts the supporting liquid a sealing layer is obtained. As a matter of fact, a certain contact time is required, so that the closing of the hose in the immediate neighbourhood of the communicating slit will be incomplete, and the danger of lateral deformation and penetration of liquid will remain in that zone.

Athough the latter method is satisfactory in many cases, it has proved to be insufficient in those cases where the samples should comply with very strict requirements as to undisturbedness and composition. Therefore, an improvement is needed in this respect.

The invention provides, to that end, a pre-coated hose, making the application of said supplementary components unneccessary. Said hose is characterized by a finely meshed elastic network, e.g. a knitted pipe, which network has previously been processed in such a manner that the deformability thereof in the longitudinal direction is small compared to that in the transverse direction, whereas the deformation in the transverse direction tends to be smaller as the hose is stressed more in the longitudinal direction, and is further characterized by a coating previously applied to said network, said coating sealing off the openings in the knitted fabric, and being adapted to join the deformation of said knitted fabric.

When applying such a hose for taking a soil sample care is taken that the friction between said hose and the exit slit of the chamber is sufficiently high, so that a certain longitudinal tension load in the hose is obtained causing a transverse deformability to be removed, or at least to be substantially lowered. In this manner the supporting effect of the supporting liquid is enhanced, which is important when the sample is Stratified and the various layers thereof show a different lateral deformation. The supporting liquid then provides a given minimum counter pressure, whereas the hose provides the supplementary support. A first requirement is that the diameter of the hose is not reduced owing to said longitudinal load.

More specifically, the sealing coating layer of said hose may consist of a substantially elastomeric substance, e.g. synthetic or natural rubber or mixtures thereof. Such coatings should, moreover, have stretch properties of such a kind that the desired stretch behaviour which has already been achieved by the previous treatment, is further improved.

The method for taking a soil sample may specifically be executed in such a manner that the friction between the hose and the communicating slit is such that the longitudinal tensile lead of the hose is suflicient to remove the transverse deformability or to reduce it so much that,

together with the hydrostatic pressure of the supporting liquid, the outward deformation of the sample is prevented.

The sampler according to the invention for performing said method, comprising a chamber for holding said hose and being concentrically arranged around a sample tube and communicating with the interior of said tube by means of a circumferential slit, is characterized in that the outer wall of said chamber is gradually rounded towards said circumferential slit in order to provide a large contact area between the hose pressed outwards by the supporting liquid and said wall. More specifically, a plurality of communicating passages between the interior of said sample tube and said chamber may be provided at a small distance above said slit in order to facilitate the penetration of said supporting liquid into said chamber, causing the hose to be pressed against the wall of said chamber and the friction to be increased, which passages may also be provided at a higher level between the interior of the sample tube and the chamber, so that said supporting liquid may penetrate in between the inner wall of said chamber and said hose in order to reduce the friction in that region.

The method according to the invention for manufacturing a hose of this kind is characterized by the fact that a circularly knitted pipe or a similar fabric is previously treated to make the longitudinal deformability smaller than the transverse one, and to make the latter inversely dependent on the longitudinal tensile load, said knitted pipe or the like being subsequently pulled through a liquid containing a substantially elastomeric substance or is made thereof, the knitted pipe coated with this liquid being finally kept at some longitudinal tensile load to the desired diameter sufiiciently long for the coating to stabilize.

Since the knitted pipe after having been pulled through said liquid is kept at a longitudinal tensile load, the molecules of said elastomeric substance may be aligned in the same direction, which will contribute to the desired stretch behaviour.

Said liquid may be a volatile solvent or suspending agent for the elastomeric substance, or may consist of a liquid monomer which may be heat-polymerized, the stabilization of said coating being effected by evaporation of the solvent in the former case and by polymerization accelerated by heat in the latter case.

Preferably, heated air is blown into said knitted pipe under a suflicient pressure for substantially maintaining the desired diameter, at least during the stabilization period, and, at the same time, the temperature of said air may promote said stabilization.

Said method may be effected more in particular in such a manner that the knitted pipe is guided around a ring at least partially immersed in said liquid, thus b ing stretched to a given diameter, and is subsequently pulled at a given velocity from said liquid by means of a suitable pulling device, the diameter of said ring, the pulling rate, the composition of said liquid and the structure of said knitted pipe being mutually matched in such manner that the ready hose will show the desired stretch properties.

The tensile stress occurring in the coated hose will then depend upon the friction between the knitted tube and said ring and possibly other surfaces. Said tensile stress is important for aligning the molecules in the coating.

The coating liquid may especially contain a solution or an emulsion of a natural or synthetic rubber or a mixture thereof. If so desired a non-elastomeric thermoplastic substance and, if necessary, a plasticizer and a polymerization catalyst may be added. In this manner the result may be that the finished hose after its folding in the chamber of the sampler will undergo a certain permanent deformation so that an exactly sufficient elasticity is left to have the hose fit around the sample without any substantial stress. The original diameter of the uncoated 4 knitted pipe will, then, be less critical. The said polymerization agent acts as a vulcanizing agent for the rubber, so that the directed stabilization of the layer applied upon the knitted pipe will be promoted under the influence of the tensile stress exerted thereon.

The apparatus according to the invention for practicing this method is characterized by a tray for containing the coating liquid, said tray being provided with a central opening with a smooth upright rim, by a ring concentrically attached to said smooth rim which is fixedly attached and separated from the bottom of said tray, by a tube protruding through said opening and connected to said ring, said tube being provided with lateral passages in the part above said ring and being closed at its upper end, by an inner tube placed inside said tube, and having its opening above the latter tube, the intermediate space between both tubes being connectable to an air supply, and the interior of said inner tube being connectable with an air exhaust, and by a means for pulling the knitted pipe or the like upwards, said knitted pipe being supplied from below and around the first tube, and subsequently being guided over the rim and around said ring through the liquid present in said tray.

More specifically, an electrical heating element may be present in the air supply duct between the two tubes, whereas, moreover, above said tray and at some distance of the outer tube one or more heating elements such as infra-red radiating means may be arranged.

The pulling means of this apparatus may comprise a circular disc, the diameter of which being substantially equal to the outer diameter of said ring, which disc is connected to a drawing string or the like which may be pulled upwards at the desired rate, but it is also possible for this pulling means to comprise a winding reel for the coated hose, and a guiding ring may, if necessary, be arranged between the ring in said tray and this reel, the outer diameter of the latter ring being substantially equal to the outer diameter of the former ring.

The invention will now be described in detail with reference to the drawings, in which:

FIG. 1 shows diagrammatical cross-section of the lower part of a soil sampler according to the invention; and

FIG. 2 a diagrammatical cross-section through an apparatus for coating a hose, which may be used in the soil sampler according to FIG. 1.

The soil sampler shown in FIG. 1 comprises an outer tube 1 and a concentrical inner tube 2, said tubes delimiting together an annular chamber 3. The outer tube ends at its lower extremity in a cutting edge 4, which is pushed into the soil, so that a soil sample 5 may penetrate into the inner tube.

In the chamber 3 an elastic hose 6 is present in folded condition. At the lower end of the chamber 3 said hose is passed through a circumferential slit 7, communicating with the interior of the inner tube 2. Inside this tube the hose is closed by means of a knot or a clamp as indicated at 8. During the taking of a soil sample this extremity of the hose is maintained at a fixed level in respect of the surrounding soil by means of a string or the like, and will, therefore, move in respect of the inner tube 2. The soil sample penetrating into the soil sampler is, then, surrounded by the hose which is gradually extracted from the chamber 3.

Since between the hose and the wall of said slit 7 friction will occur when the hose leaves the chamber 3, said hose will be submitted to a tensile load inside the tube 2 which is dependent on the friction.

The hose according to the invention consists of a knitted pipe, e.g. from nylon yarn, which has been submitted to a preliminary treatment by which the deformability in the longitudinal direction is considerably lowered compared to the deformability in the transverse direction. Owing to this transverse deformability the hose may be easily folded in the chamber 3. Said hose should, however, fit tensionless around the sample. The knitted pipe is manufactured in such a manner, that when exerting a tensile load no contraction occurs, but the stretchability in the transverse direction is lowered in function of the tensile load.

The pressure of the supporting liquid 9 should be transferred to the sample, and in particular to the grain skeleton thereof. This is only possible when the hose is impermeable. In the known soil samplers, to that end a liquid is introduced into the chamber in which the hose is stored, which liquid may seal off the meshes of the knitted fabric of said hose as soon as said liquid contacts the supporting liquid. With the hose according to the invention, which is provided with an impermeable elastic coating, said pressure transfer is ensured per se. Moreover, such a hose prevents the penetration of supporting liquids into the sample over the entire length, or conversely, the egression of components of the sample into the supporting liquids.

When taking a soil sample it is not known in advance how the sample is composed. In the case of a stratified soil the risk of deformation, and the counter pressure required in each case, are not the same everywhere, so

that it is not possible to select a supporting liquid providing the desired counter pressure all over. When the pressure of the liquid would be too high, the sample might be locally compressed, which is unacceptable. The hose according to the invention makes it possible to remove this objection completely or at least substantially.

With the hose according to the invention an outward deformation in the transverse direction is prevented when a tensile load in the longitudinal direction is exerted up to a predetermined transverse tension, wherein the value of said maximally supportable transverse tension depends on the longitudinal tension. In the case where the supporting liquid supplies the required minimum supporting pressure, it will be possible by exerting a suitable tensile force on the hose that the internal friction of the various layers which produces different transverse tensions will be within the range of transverse tensions to be supported by the hose. As the transverse tensions in the sample are proportional to the longitudinal tensions, which again depend on the depth, the longitudinal tension of the hose should increase with the depth. This may be achieved by a special construction of the soil sampler according to the invention.

The soil sampler according to FIG. 1 differs from the usual soil samplers in that, on the one hand, the wall of the chamber 3 where the slit 7 is found, is gradually rounded, and in that, on the other hand, at a small height above said slit a number of passages 10 are provided connecting the lower part of said chamber with the interior of the tube 2. The hose 6 will now be pressed against the rounded wall by the hydrostatic pressure of the supporting liquid, so that the friction will be increased in function of the pressure of said supporting liquid which, again, is proportional with the depth. In this manner the tensile tension in the hose may be adapted to the desired supporting effect.

Furthermore, additional passages 10 may be provided between the chamber 3 and the interior of the tube 2 in order to allow the supporting liquid to penetrate into said chamber at the inner side of said hose, so that the friction between said hose and the inner wall of said chamber is lowered. This is, in fact, important, since without said lowering the friction will be most at the beginning and the least at the end of the operation, which is exactly not desired. As shown the rounding of the wall of the chamber near the slit 7 will be deepened so much that the hose may emerge substantially tangentially to the sample.

FIGURE 2 shows a diagrammatical cross-section of an apparatus for manufacturing a coated hose according to the invention. This apparatus comprises a tray in which a liquid 12 is present which is used for coating a circularly knitted pipe 13. Said tray '11 comprises a central opening with a circular upright rim 14. A11 outer tube 15 pro- 6 trudes through said opening, and within said tube an inner tube 16 is arranged. An upright ring )17 is connected to said outer tube, which ring extends into the liquid 12 and ends at some distance from the bottom of the tray 11. Above said ring 17 passages 18 are provided in the tube 15, the latter being closed at the upper end, and the inner tube 16 having its opening above said closed end. The space between both tubes is connected with a compressing pump or the like, whereas the inner tube forms an air exhaust; the air flow is indicated by means of arrows. Around the tube -16 a heating element 19 has been indicated by means of which the supplied air may be heated. Moreover, heating elements 20 in the form of infra-red radiators or the like may be arranged on the outside of the assembly.

The knitted tube 13 to be coated is guided over the rim 14 and under the ring 17, and is subsequently connected to a disc 21 having a diameter which is substantially equal to the diameter of the ring 17. By giving the introduced air a slight extra pressure, the knitted pipe between the ring and the disc may be easily maintained at a given diameter. Said disc 21 may be pulled upward by means of a string 22 which is guided over pulleys 23 and at its other extremity is connected to a weight 24. The velocity thereof is depended on the friction between the pipe 13 on the one hand, and the rim 14 and the ring 17 on the other hand, and, therefore, also on the diameter of said ring. Said pipe will be coated with a liquid layer, which is stabilized to a coherent coating under the influence of the hot air and/or the heat radiation, so that a coated hose 6 according to the invention is obtained.

The liquid 12 contains to that end a substance which is able to form a coating with the desired properties. As a consequence of the friction mentioned above the portion of the hose above the liquid 12 is submitted to a given tensile stress. Said stress promotes the alignment of the molecules of said coating substance during its stabilisation which will further improve the stretch properties of the hose mentioned before.

Substantially elastomeric substances have proved to be very suitable for coating the knitted fabric. Examples of such substances are synthetic and natural rubbers or mixtures thereof. Said substances may, for example, be dispersed in a volatile solvent or suspending agent, after which the liquid so obtained is introduced into the tray 11. Said solvent or suspending agent evaporates on heating, leaving behind a layer of the dissolved substance. It is also possible to start with a liquid monomer which, possibly with the aid of catalysts and/ or accelerating agents, quickly polymerises by the action of heat, in which case the heating elements 20 are necessary for a quick stabilisation of the coating. Moreover, scrapers 25 may be desirable in order to maintain a desired uniform thickness of the layer.

The apparatus of FIG. 2 may, alternatively, be constructed in such a manner, that the coated hose 6 is wound on a reel at some distance above the tray. If necessary a guiding ring may also be mounted at some suitable point inside the hose the outer diameter of which is equal to that of the ring 77.

As mentioned before, the hose 6 should be sufficiently transversely stretchable to be folded in the chamber 3, but should also fit smoothly around the sample without substantial transverse tension. To that end the coated hose should be modeled in the apparatus of FIG. 2 to about the diameter of the soil sample. If, now, a substance is added to the liquid 12 which experiences a permanent stretch upon loading, the result may be that the hose assumes a slight permanent stretch during its tensioning in the chamber 3 which is such that the hose will fit around the soil sample in the desired manner, although the original diameter of the hose was less. In this manner the starting material may be less critical. Furthermore, the stabilisation of the coating layer may be influenced by the addition of a polymerisation catalyst or the like.

The dimensions of the apparatus according to FIG. 2, the pulling rate in this apparatus, the nature of the knitted pipe and the composition of the coating substance, should be mutually matched in such a manner that the ready hose obtains the desired properties which, of course, depend on the application in view.

One may start, for example, wtih a hose of nylon yarn which is guided through a bath containing a vitreous thermoplastic substance with a plasticizer, a synthetic rubber and a solvent, to which, if desired, a vulcanizing agent for the rubber may be added.

The vitreous thermoplast which is softened by the plasticizer eifects a certain permanent deformation of the hose, the original diameter being too small for the soil sample in question. The vulcanizing agent sees to the stabilization of the molecules in the direction determined by the tensile stress in the apparatus of FIG. 2. In some cases the plasticizer appears to be entirely redundant.

This example is, naturally, not intended in a restrictive sense, since it will be clear to one skilled in the art that numerous other substances may be found which are suitable to such coating.

In this maner soil samples may be taken, which fully correspond with the composition of the soil, for which, nevertheless, no other expedients are required than a simple supporting liquid.

We claim:

1. A sampling means for taking an undisturbed soil sample comprising a hose which is deformable in the transverse direction and has little deformability in the longitudinal direction, the deformation in the transverse direction being inversely dependent upon the amount of stress on the hose in the longitudinal direction;

an outer tube;

an inner tube disposed within the outer tube so as to form an annular chamber therebetween wherein the hose is partially contained, the inner tube has a circumferential exit port through which the annular chamber communicates with the interior of the inner tube, the annular chamber has an inner and an outer wall;

means for inserting the sampling means into soil whereupon the soil sample penetrates Within the inner tube, pulls the hose through the exit port and out of the chamber and contains itself at one end within the hose;

means for closing off the other end of the hose so as to encase the soil sample within a portion of the hose without exerting a substantial pressure on the sample while maintaining the closed end of the hose at a constant level in respect of the surrounding soil;

a supporting liquid contained between the inner tube and the hose, which hose is substantially impervious to the supporting liquid and to the components of the soil sample, the supporting liquid being present in sufficient quantity to produce a head of pressure causing the hose to be pressed against the chamber wall and increasing friction as a function of the pressure of the supporting liquid;

means for removing the soil sample from the soil while maintaining sufficiently high friction between the hose and the exit port so that the longitudinal tensile load of the hose together with the hydrostatic pressure of the supporting liquid is suflicient to prevent outward deformation of the sample.

2. A sampling means as described in claim 1 wherein the outer wall of the chamber is gradually rounded towards the circumferential exit port.

3. A sampling means as described in claim 1 further including a communicating passage between the interior of the inner tube and the chamber at a small distance above the exit port, said passage serving to facilitate penetration of the supporting liquid into the chamber, to cause the hose to be pressed against the wall of said chamber and thereby increase friction.

4. A sampling means as described in claim 1 further including a passage between the interior of the inner tube and the chamber, said passage being provided at a distance above the exit port sufiicient to permit penetration of the supporting liquid between the inner wall of the chamber and the hose in order to reduce friction in that area.

5. A sampling means as described in claim 1 wherein said hose is knitted and comprises a finely meshed open network and the openings in the network are sealed with a coating material which renders the hose impervious to the supporting liquid.

6. A sampling means as described in claim 5 wherein the coating material is a substantially elastomeric substance.

7. A method for taking an undisturbed soil sample comprising the steps of inserting a first tube into soil; the first tube is disposed within a second tube, the space therebetween defining a chamber wherein a hose is normally partially contained, the hose is deformable in the transverse direction and has little deformability in the longitudinal direction, the deformation in the transverse direction being inversely dependent upon the amount of stress on the hose in the longitudinal direction, the first tube has a circumferential exit port through Which the chamber communicates with the interior of the first tube whereby the soil sample penetrates within the interior of the first tube, pulls the hose through the port and out of the chamber and contains itself at one end within the hose;

closing off the other end of the hose so as to encase the soil sample within a portion of the hose without exerting a substantial pressure on the sample while maintaining the closed end of the hose at a constant level in respect of the surrounding soil;

introducing a sufficient quantity of supporting liquid between the first tube and the hose to produce a head of pressure, said hose being substantially impervious to the supporting liquid and to the components of the soil sample whereby the hose is caused to be pressed against the chamber wall thereby increasing friction as a function of the hydrostatic pressure of the supporting liquid;

removing the soil sample from the soil while maintaining sufficiently high friction between the hose and the exit port so that the tensile load in the longitudinal direction of the hose together with the hydrostatic pressure of the supporting liquid is sufiicient to prevent outward deformation of the sample.

References Cited UNITED STATES PATENTS 3,312,568 4/1967 Coker et al 117-94 X 3,157,544 11/1964 Lichtey l1794 X 2,879,803 3/1959 Francois 11794 X 2,602,959 7/1952 Fenlin 11794 2,927,775 3/ 1960 Hildebrandt 245 2,927,776 3/1960 Hildebrandt et a1. 175-245 FOREIGN PATENTS 1,107,204 4/ 1955 France.

DAVID H. BROWN, Primary Examiner US. Cl. X.R. 175-245 

